The present invention relates generally to steering systems for automotive vehicles, and more particularly, to a misalignment detection system for the steering system.
During operation of an automotive vehicle, the steering system may become misaligned. Misalignment can occur in an automotive vehicle for various reasons. Particularly in states with harsh winters, potholes and rough roads can cause the steering system to become misaligned.
A misalignment in the present application refers to a misalignment of the steering wheel with the desired direction of travel as set forth by the steering assembly. Misalignment as noticed by the driver occurs when the steering wheel is held in a straight ahead direction and the wheels tend to cause the vehicle to drift away from the directly straight ahead path.
Oftentimes, the misalignment is slight. However, the effects of the misalignment may manifest themselves in the vehicle. For example, a misaligned steering system may cause excessive wear on one portion of the tires. Until such wear is noticed by the vehicle operator, the alignment may go uncorrected. Unfortunately, the excessive wear may require the tires to be prematurely changed due to uneven wear.
It would therefore be desirable to provide a misalignment detection system for an automotive vehicle that signals the driver to the presence of a misalignment so that corrective actions may be taken.
The present invention provides a misalignment system for a steering system of an automotive vehicle that includes a velocity sensor that generates a vehicle velocity signal indicative of the vehicle velocity. A yaw rate sensor generates a yaw rate signal indicative of the yaw rate of the vehicle. A memory stores a steering ratio memory map and a historic steering wheel angle. A controller is coupled to the velocity sensor, the yaw rate sensor, and the memory. The controller estimates a current steering wheel angle at a predetermined velocity. This estimated steering wheel angle is a function of the vehicle velocity, the yaw rate, and a steering ratio. The controller compares the current steering wheel angle with a historic steering wheel angle to determine an error.
One feature of the invention is that upon a predetermined amount of accumulated error, the vehicle operator may be presented with an indicator to inform him of the misalignment.
In a further aspect of the invention, a method for determining misalignment comprises the steps of:
detecting a vehicle speed;
detecting a vehicle yaw rate;
determining a base steering wheel angle at a predetermined vehicle speed as a function of yaw rate;
determining an error between the base steering wheel angle and a historic steering wheel angle; and
indicating an error if the error is above a predetermined level.
One advantage of the invention is that by signaling the vehicle operator of a misalignment, excessive wear to a vehicle""tires or other components may be reduced by corrective action. Another advantage of the invention is that many of the sensors are currently used in other systems of the vehicle. Therefore, implementation of a misalignment detection system according to the present invention may be done in a cost efficient manner.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.